1. Technical Field
Embodiments exemplarily described herein relate to a semiconductor device and a method of fabricating the same, and more particularly, to a semiconductor having a storage node electrode and a method of fabricating the same. The semiconductor device may comprise a DRAM having a capacitor structure.
2. Description of the Related Art
Semiconductor devices, for example, DRAMs, are highly integrated and have high capacitance. To increase the capacitance of a highly integrated DRAM, more capacitors are arranged in a limited area and capacitors with higher capacitance are used. Accordingly, the density and height of storage node electrodes in the capacitors have increased.
For example, a DRAM cell having a cylindrical storage electrode is disclosed in U.S. Pat. No. 6,855,597 issued to Shin Chul-Ho et al. In the DRAM cell, a dielectric film is formed on an outer surface as well as an inner surface of a storage node electrode. Accordingly, the area of the dielectric film and the capacitance of a capacitor are increased. The storage node electrode may be formed of a doped polysilicon. However, the capacitance of the capacitor may decrease due to depletion of a dopant in the polysilicon.
To address this problem, a metal film is used as the storage node electrode. For example, a metal nitride film, such as a titanium nitride film, is used as the storage node electrode. The metal nitride film is formed by a chemical vapor deposition (CVD) process rather than a physical vapor deposition (PVD) process due to step coverage. However, the metal nitride film formed by the CVD process has a columnar grain structure with low density.
Thus, the metal nitride film with the columnar structure may be susceptible to penetration of a wet chemical and oxygen. When the wet chemical penetrates into the metal nitride film and reaches a lower region of the metal nitride film, an insulation film and a contact plug that underlie the metal nitride film may be etched, thereby generating a void. The oxygen penetration into the metal nitride film may also oxidize the metal nitride film, thereby increasing a resistance of the metal nitride film. The generation of a void may significantly decrease the reliability of the DRAM, for example, causing a circuit disconnection.
FIG. 1 shows a void generated when a titanium nitride film is used as the storage node electrode. A titanium nitride film 80 is formed on a semiconductor substrate 60 by CVD to interpose an insulation film 70 therebetween. The titanium nitride film 80 has a columnar grain structure. Thereafter, a resultant substrate on which the titanium nitride film 80 is formed is treated with a wet chemical, for example, a diluted HF solution, for a predetermined time, and then its cross-section is observed by an electron microscope. A void generated due to etching of the insulation film 70 is observed in a region B under the titanium nitride film 80, as illustrated in FIG. 1. That is, the wet chemical penetrates below the storage node electrode that is formed of the titanium nitride film, and thus a void may be formed under the storage node electrode.